X-ray absorption and x-ray magnetic dichroism study onCa3CoRhO6andCa3FeRhO6

Abstract

By using x-ray absorption spectroscopy at the $\text{Rh}\text{ }{L}_{2,3}$, $\text{Co}\text{ }{L}_{2,3}$, and $\text{Fe}\text{ }{L}_{2,3}$ edges, we find a valence state of ${\text{Co}}^{2+}/{\text{Rh}}^{4+}$ in ${\text{Ca}}_{3}{\text{CoRhO}}_{6}$ and of ${\text{Fe}}^{3+}/{\text{Rh}}^{3+}$ in ${\text{Ca}}_{3}{\text{FeRhO}}_{6}$. X-ray magnetic circular dichroism spectroscopy at the $\text{Co}\text{ }{L}_{2,3}$ edge of ${\text{Ca}}_{3}{\text{CoRhO}}_{6}$ reveals a giant orbital moment of about $1.7{\ensuremath{\mu}}_{B}$, which can be attributed to the occupation of the minority-spin ${d}_{0}{d}_{2}$ orbital state of the high-spin ${\text{Co}}^{2+}$ $(3{d}^{7})$ ions in trigonal prismatic coordination. This active role of the spin-orbit coupling explains the strong magnetocrystalline anisotropy and Ising-type magnetism of ${\text{Ca}}_{3}{\text{CoRhO}}_{6}$.